There has developed in recent years different methods to extend the lifetime of wood telephone and power line poles by surrounding the pole at the ground level with a protective sleeve which holds the pole in a secured arrangement so that the pole may be continued in service. It is common for these utility poles, prior to placement in the ground, to be treated with a preservative, such as creosote. Creosote protects the pole against termites, wood rot, and other elements in the soil which are destructive to the integrity of the wood of utility poles, however, after a period of years, the creosote protection wains and the elements, both in the earth and in the air, begin to attack and rot and decay the wood of the pole. In most cases, and depending upon the type of soil that the pole is resting in, the pole will experience its most severe rot and decay at or just below the ground level. Pole decay generally starts immediately below ground line, works down to an expected depth of approximately 18 inches, and up the pole at a slow rate.
In the past, the process has been to replace the pole with a new pole, or to saw the existing pole off near the ground line and place a second pole into the ground nearby, then piggy-back the old pole to the stub of the new pole sticking out of the ground with strapping. As mentioned above, there has been progress in placing split sleeves around the telephone poles whereby a circular area around the pole is dug out by hand, the split sleeve assembled around the pole, and then the volume evacuated outside the new sleeve filled in. The sleeve surrounding the pole may engage the pole in a tight or compression configuration, or the sleeve may have an annulus between the outer diameter of the pole and the inner diameter of the sleeve, the annulus then filled with a mixture of sand, soil, aggragate, and chemicals to preserve the pole. In such case, the usual procedure is to emplace the sleeve approximately 3 feet below the soil level (past the point of usual decay), with the sleeve rising into the air another 3 feet (also past the area of usual decay). The portion of the pole below the 3 foot depth has usually maintained its integrity, as well as the portion of the pole above the 3 foot height above ground level.
The rule of thumb for pole emplacement is that approximately 1/5th. of the length of the pole is buried into the ground, although this general formula may be varied depending on the type of ground encountered. Obviously, in sandy soil, the pole depth would need be more than 20% of its length, while in extremely hard rocky soil, the pole depth may be less than 20% of its length.
It is apparent that the method of placing a sleeve around the utility pole is a preferred method since, in most cases, it is much more economical than pole replacement, and doesn't suffer from the problems which are going to be incurred again where a piggy-back pole into the ground arrangement is utilized. In most cases, the sleeve is made from steel, and can be precoated with a rust inhibitor in order that it lasts for a long period of time. However, the sleeve method may be costly if the annulus around the utility pole has to be evacuated by hand methods. If it were possible to utilize the sleeve itself as a tool for evacuating the annulus of soil between the pole and the sleeve, the benefit is obvious. It is to such a split sleeve, which will evacuate an annulus of soil around a standing utility pole, the subject invention is directed.